Okay as a guy who just bought an 05 GSXR600 the other day i have to weigh in on the 600 vs 100 debate.
Now i weight about 210-215 depending on the day and am 5'10" and my bike is all stock in the power department. If i am in the upper rev range and even twist the throttle a little too much the bike wants to lift the front wheel and accelerates at a crazy rate.
Now i have been riding bikes since i was 10 (i am 20 now) and had an older 185 Honda Enduro before this and i was able to do wheelies and really get on it. But on the 600 i do everything i can to avoid it just becuase it seems like it has the power to get away from me.
For those people that consider buying a GSXR 600, I want to get into more detail about this comment (specifically the "wheel lifting" part):
If you are in the "upper" rev range you are there because you want to be.
Unless you have just no clue about motorcycles and don't know that you have a serious powerplant under your ass. Cause in that case you're definately sitting on the wrong bike
But since you are reading this post here, you most likely don't fall into the "no clue" category.
I've been riding a GSXR 600 K6 for about 2 months now. The last time I rode a bike before was about 11 years ago when I did my driving licenses. So I am a newbie rider, but I can tell you about my experience with the 600.
If I just cruise around I am running at around 4-5K rpms with a higher gear.
If you pull on the throttle at cruising rpms nothing much happens. Probably less than on a touring bike that has 70hp and more low end torque.
The GSXR starts pulling harder at around 8K.
I have only tried to get the front wheel off the street like 3 times until now (1st gear, on my way to work) and it never left the ground. I thought I had given it quite a lot of throttle but the wheel did not lift.
Now this is probably the advantage of someone that starts out on a bigger bike, is aware of what he is driving and respects it.
Someone coming from a smaller bike might just open up the throttle a lot more then I am because he is used to doing that from his old, slower bike.
So if you are aware of what you are riding, this bike definately won't drop you off everytime you give it some gas.
Anyway, if you buy such a bike you are most likely a person that "wants" to go up to 12 or 14k rpm from time to time (when passing slower cars, just for the fun of it, or whatever reason). I have as well, but still, my front wheel never lifted since I ride my Gixxer.
And the power you get up in that rev range is really much more than enough. You don't "need" a Liter Bike.
Hope this info helps someone.
Stay safe and have fun